1. Field of the Invention
The present invention relates to robotics and, more particularly, to a robot using tendons to position and orient a platform in a work space.
2. Description of the Prior Art
The shape of a robot has long been divorced from a form which is human-like, and presently is determined solely by the robot's function and the laws of physics. For many applications, the robot is nothing more than a platform which can be moved throughout a work space. An end effector mounted on the platform is designed to perform a specifics task, such as grasping loose articles or holding and manipulating a tool.
The generic problems are to position and properly orient the platform and attached end effector throughout the work space with speed and accuracy. Furthermore, the platform must not only be accurately positioned, but must be sufficiently rigid in that position so as to controllably apply the required force to the end effector or support the mass of a payload. Finally, the robot should be reconfigurable and portable so that it may perform tasks in work spaces of varying shapes, as well as in different locations.
There are a number of robotics apparatus which use tendons to position a platform in a work space, for example, U.S. Pat. No. 4,873,571 issued to Balet et al. Common to the tendon suspended platform robots of the prior art is the use of distal reels to control the position of the platform by controlling the length of the tendon extended from each reel. More particularly, the reels are respectively situated at the distal ends of the tendons located along the periphery of the work space, with the proximal ends of the tendons being attached to the moveable platform. This design requires suitable sites to allow for the secure anchoring of the distal reels.
The drawbacks inherent to such apparatus are difficulty In relocating the robot because each move requires moving and reanchoring each reel. Moreover, even changing the work space at the same location requires relocating at least one reel. As the size and weight of the distal reels are proportional to the size of the platform and the maximum force it may apply, the foregoing considerations effectively limit the portability and ability to reconfigure the robot, or the maximum force or payload of the robot. In essence, distal reels require a design compromise, and preclude the use of a tendon suspended platform robot for many applications.
Tendon suspended platform robots using distal reels typically provide only for the translation of the platform along three axes. Rotational degrees of freedom for the end effector are customarily provided by mounting a rotational apparatus on the platform which is gimbaled relative to the platform, and attaching the end effector to the rotational apparatus. However, this solution introduces a completely different device to the suspended platform, adding complexity to the physical apparatus as well as to the control system, which must coordinate the operation of the two apparatus.